Imaging of current in internal conductors through magnetic field detection by magnetic force microscopy (MFM) is of growing interest in the analysis of integrated circuits (ICs). This thesis presents a systematic study of the MFM based mapping of current in model circuits by using force and force gradient techniques. In comparing these two techniques, force was found to have a much higher signal to noise ratio (from ~150 to ~580 times) than force gradient at large tip-sample distances considering the presence of thick overlayers in ICs. As a result, force will have better sensitivity and can therefore be used to detect much smaller minimum currents. We have achieved a sensitivity of ~0.64 µA per square-root Hertz in air and ~0.095 µA per squre-root Hertz in vacuum for force with a pinning field with a probe-circuit separation of 1.0 µm. We conclude that the force technique is superior for the application of MFM current imaging of buried conductors, albeit with reduced spatial resolution. Numerical modeling of the MFM images has shown that the simple point probe approximation is insufficient to model MFM images. An extended model, which considers realistic MFM probe geometries and the forces acting on the whole probe, has been shown to be necessary. Qualitative and quantitative comparisons of the experimental and simulation results with this model are in agreement to within experimental uncertainty. The comparisons suggested that the CoCr film thickness is not uniform on the probe, which was verified by scanning electron microscope cross-section images of the probes cut by a focused ion beam. Most notably, the CoCr film was 1.5 times thicker on the cantilever than on the tip. Based on the simulation and experimental results, we have devised a method to accurately locate the current path from MFM images with submicrometer uncertainty. The method was tested for different patterns of model conducting lines. It was shown to be a useful technique for fault location in IC failure analysis when current flows through the devices buried under overlayers and no topographic features are on the surface to provide clues about the positions of the devices.

Our main objective in this thesis is to investigate three methods: Principal Component Analysis, Vector Space Model, and Signal Analysis, to establish system behaviours of an electromechanical system based on its historical operation data. The system behaviours are constituted by an aggregate number of similar actions which can be represented as patterns or clusters. The results show that we are also able to observe normal behaviours by interpreting a high percentage of similar actions inside patterns or clusters. Any deviations from the established normal behaviours could be interpreted as abnormal which warrant further investigation with respect to fault pre-emption and detection.

The stator inter-turn faults can result in catastrophic failure of the electric machines leading to extended downtime of the equipment, increased cost of repair and heavy financial losses in the industries. In the recent trends, online fault diagnosis of the electric machines that arc employed in critical applications has been considered very important since frequent outage of the machines for the purpose of testing cannot he recommended. In this work. diagnostic tools have been developed to unambiguously detect the early stages of these limits in the salient-pole synchronous machines. both reluctance synchronous machine and synchronous machine with DC excitation. Motor current signature analysis. a very useful tool in the condition monitoring of electrical machines. has been primarily used for this purpose. This study mainly consists of development of theoretical background for the diagnostic schemes followed by the implementation of these schemes on both simulated and experimental machines. For this purpose. detailed mathematical models of the synchronous machines have been developed that can include stator inter-turn faults with desired fault severity. The developed models can also accommodate some structural asymmetries of the machines. These models have been instrumental in testing the proposed diagnostic schemes under ideal conditions. Also. reversible stator inter-turn faults have been carefully created in the experimental machines to test the feasibility of the diagnostic schemes under practical conditions. In order to ensure unambiguous fault detection. a detailed analysis has been performed under various possible abnormal operating conditions of the machines such as supply unbalance. time harmonics and internal asymmetries of the machines. Initially. certain drawbacks have been identified in a diagnostic scheme based on negative sequence quantities of the machine and critical improvements have been suggested to enhance its sensitivity. However, the modified method fails to detect faults involving one turn short. Hence a frequency domain approach has been considered to detect these faults. As a first step in this direction, it has been demonstrated that the triplen harmonics in the line current of synchronous machines cannot detect these faults unambiguously. Subsequently, owing to the stored magnetic energy in the machine after supply disconnection, it has been observed that the triplen harmonics in the terminal voltages of RSM can be useful for unambiguous detection of stator inter-turn faults. A new and very effective technique of online fault detection. based on the monitoring of some specific frequency components in the field current. has been developed for the synchronous machines with DC excitation. This scheme uses the structural asymmetries of the field winding. Similar results have also been realized using a rotor-mounted search-coil with very high sensitivity. In this work, an instrument has also been devised to implement fault diagnosis on machines using the computational capabilities of digital signal processors.

Transmission lines of any voltage level are subject to faults. To speed up repairs and restoration of power, it is important to know where the fault is located. A fault location algorithm’s result is influenced by a series of modeling equations, setting parameters and system factors reflected in voltage and current inputs. The factors mentioned are subject to sources of uncertainty including measurement and signal processing errors, setting errors and incomplete modeling of a system under fault conditions. These errors have affected the accuracy of the distance to fault calculation. Accurate fault location reduces operating costs by avoiding lengthy and expensive patrols. Accurate fault location speeds up repairs and restoration of lines, ultimately reducing revenue loss caused by outages. In this thesis, we have reviewed the fault location algorithms and also how the uncertainty affects the results of fault location. Sensitivity analysis is able to analyze how the variation in the output of the fault location algorithms can be allocated to the variation of uncertain factors. In this research, we have used global sensitivity analysis to determine the most contributed uncertain factors and also the interaction of the uncertain factors. We have chosen Analysis of Variance (ANOVA) decomposition as our global sensitivity analysis. ANOVA decomposition shows us the insight of the fault location, such as relations between uncertain factors of the fault location. Quasi regression technique has also been used to approximate a function. In this research, the transmission line fault location system is fitted into the ANOVA decomposition using quasi regression. From the approximate function, we are able to get the variance of the sensitivity of fault location to uncertain factors using Monte Carlo method. In this research, we have designed novel methodology to test the fault location algorithms and compare the fault location algorithms. In practice, such analysis not only helps in selecting the optimal locator for a specific application, it also helps in the calibration process. / Thesis (M.Eng.Sc.) -- University of Adelaide, School of Electrical and Electronic Engineering, 2009

Thesis (M.S.)--University of Texas at El Paso, 2005. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (M.S.)--Ohio University, June, 2000. / Title from PDF t.p.

Thesis (M.S.)--Rochester Institute of Technology, 2009. / Typescript. Includes bibliographical references (leaves

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 143-149). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 143-149). Also available on the Internet.

Thesis (M.Eng.(Control Engineering))--University of Pretoria, 2008. / Summary in English. Includes bibliographical references.